$M{M}^2$ has a queuing problem where customers who line up to pay their selections form the waiting line. The MM ${?}^2$ system consists of an arrival rate of $24$ per hour according to a Poisson distribution, and service times are on average equal to $2$ minutes per customer.

What is the average waiting time in the queue in minutes?

$$ a$.10$

b$.0\mathrm{.}36$

C$.4$

d$.2\mathrm{.}4$

e$.8$